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Notes on DIY starter swap

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    Notes on DIY starter swap

    Replaced my starter motor recently. Went by ISTA's steps and the numerous DIYs available online, e.g. this and this.

    Not gonna rehash the whole thing here because ISTA and those DIYs have pretty much everything covered. Just wanted to post some things I learned:


    1. The auto-stop-start starter has fully superseded -- and is an upgrade for -- the original starter. Faster and quieter. BMW PN 12417843526 (new) or 12417843530 (reman).


    2. ISTA says you have to remove one throttle actuator. You don't. I didn't see anything that'd help me understand why ISTA calls for TA removal. The extra clearance simply isn't needed. If someone knows why ISTA calls for removing a TA, please chime in.


    3. The small screw at the top of the starter isn't necessarily a T30 and doesn't seem to be very important.

    The starter motor is held in by three screws:

    Click image for larger version  Name:	Screenshot 2021-04-27 195252.png Views:	0 Size:	45.4 KB ID:	101531

    However, only the ones labeled "2" have a torque spec (2AZ below):

    Click image for larger version  Name:	Screenshot 2021-04-27 195356.png Views:	0 Size:	4.5 KB ID:	101532

    "1" isn't even listed on any parts diagrams as far as I could see. I couldn't find it on RealOEM or anywhere else. It's a much smaller bolt than the other two. Hard to imagine it contributing substantially to holding anything together. DIYs list it as a T30 Torx; on mine it was a 5mm Allen. Of course I only realized that after using a T30 to pull it out, which slightly damaged the head of the bolt. After that, trying to torque it to 42 Nm, as some DIYs and other threads imply is the spec, would end badly. That torque spec seemed high for that bolt even if it had been unsullied. No way it takes the same torque as the much bigger bolts on the sides.

    Based on my conversation with a BMW Master Tech, the purpose of that little top bolt is probably nothing more than to hold the starter in place if you drop the trans, and it probably doesn't need more than 10-15 Nm.


    FWIW.
    Last edited by IamFODI; 04-28-2021, 04:08 PM.
    2008 M3 Sedan
    6MT, slicktop, no iDrive, 18s

    Öhlins coilovers by 3DM Motorsport
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